Transcatheter valve implantation (for example, transcatheter aortic valve implantation (TAVI)) is an evolving technology for replacement valve therapy that (i) avoids the trauma of conventional open-chest surgery, and (ii) avoids the need for heart and lung bypass. In such a technique, a stent-valve is compressed and loaded into a delivery catheter. The delivery catheter is introduced to the desired site of implantation (for example at the heart) via a percutaneous route or via minimally invasive surgery. The stent-valve is deployed into the implantation position from or by the delivery catheter, and the delivery catheter is then withdrawn.
Despite the successes of transcatheter stent-valves, technological challenges remain. One such challenge is preventing leakage of blood around the stent-valve (so called para-valve leakage). The above stents form a friction fit with the native anatomy to anchor the stent-valve in position, and are round in cross-section. However the native anatomy in which the stent is implanted is often off-round and is different for each person. Moreover, heavy calcification of the native anatomy may obstruct full deployment of any stent, and make the native anatomy even more irregular. It can sometimes be difficult to provide a perfectly sealing fit between the stent-valve and the surrounding anatomy.
In order to address para-valve leakage, it is known to incorporate an external skirt or cover as part of the stent-valve. For example, the skirt is made of compressible biocompatible material, such as paracardial tissue or PET. The thicker the material of the skirt, the more able the skirt is to occlude gaps and effect a seal. However, a disadvantage is that such skirts add to the bulk of the stent-valve. A thick skirt makes the stent-valve problematic to compress to a desirably small size for implantation.
It would be desirable to provide a technique for mitigating para-valve leakage without substantially hindering the compressibility of a stent-valve.